Immunological enhancement is defined as the prolongation of allograft survival as a consequence of the action of humoral antibody against the antigens not present in the host. In our studies on immunological enhancement, we use the SaI tumor, which is indigenous to A(H-2a) strain mice. Passive immunological enhancement of this tumor is readily achieved in allogeneic C57BL/Ks(H-2d) mice by administration of anti-SaI serum at the time of tumor inoculation. During this past year we have studied the cellular mechanisms of immunological enhancement using both in vivo and in vitro model systems. Our research efforts were concentrated in four major areas. These are: 1) the role of the target cells membrane antigens in immunological enhancement, 2) the immune response of mice during passive immunological enhancement, 3) immunological enhancement of the SaI tumor in syngeneic A/J mice and 4) scanning electron microscope examination of killer cell-target cell interaction. The overall objectives of this research program are to gain a better understanding of the cellular bases of immunological enhancement and to develop procedures for the manipulation of the immune response such that accelerated rejection of a tumor or a graft will occur under one set of conditions while immunological enhancement will occur under another set of conditions. BIBLIOGRAPHIC REFERENCE: Vincent, J.C. and Tokuda, S. Suppression of cell-mediated immunity against the Sarcoma I tumor by antiserum. New Mexico Branch American Society for Microbiology, Los Alamos, NM, 11, October, 1975.